Thread: My bevel angle calculations

Originally Posted by BeBerlin

Honing_Angles_Matrix.xls?

Robin, what type of tape are you using for these calculations? On the spreadsheet it shows that the thickness of the tape is just under a third of a centimeter, and that's some ultra thick tape. That's just under an eight of an inch for one layer, on one side.

I'd suggest using the measurements for 3M Super 33+ electrical tape. It's supposed to be 7 mil thick, but I just put on my digital calipers and I get .18 mm on average. That's 0.18 cm vs 3.0.

3M Super 33+ is quality electrical tape readily available to most on the forums. If we are going to use something as a 'standard measurement', then it should be good quality stuff, I'd think.

Originally Posted by Ben325e

Robin, what type of tape are you using for these calculations? On the spreadsheet it shows that the thickness of the tape is just under a third of a centimeter, and that's some ultra thick tape. That's just under an eight of an inch for one layer, on one side.

My bad, I thought I'd updated the file in the meantime. It's 0.3mm, not 0.3cm. Regular electrical tape.

Originally Posted by Ben325e

3M Super 33+ is quality electrical tape readily available to most on the forums. If we are going to use something as a 'standard measurement', then it should be good quality stuff, I'd think.

Absolutely, which is why I am using tesa Isolierband.

Doesn't really matter, though. Just fill in the thickness of your favourite tape in the spreadsheet, and measuring happiness will ensue.

Originally Posted by Ben325e

3M Super 33+ is quality electrical tape readily available to most on the forums. If we are going to use something as a 'standard measurement', then it should be good quality stuff, I'd think.

That is what I use. Made in Minnesota. For those of use in the USA, buy American. The job you save may be your own.

Okay......

Originally Posted by StraightRazorDave

I like it! But your new y would have to be measured again if you added tape, since it would be larger if you added tape. But it makes complete sense to me.

x = spine width
y = distance from spine/hone contact point to tip of bevel with no tape on spine
n = number of tape layers
t = thickness of tape
Θ = total bevel angle °


total bevel angle:

Θ = 2{arctan[(.5x + nt)/{ycos(arcsin{.5x/y})}]}

arcsin(.5x/y) gets you the angle on one side of the bevel, then y times cosine of the resultant angle gets you the width of the razor that I was formerly calling w.

This allows for w to remain constant no matter how many layers of tape are added, eliminating the need to 1.) remeasure the hypotenuse every time you add a layer of tape, and 2.) measure w initially, which as you pointed out could be difficult.

Note that I newly defined y. Defining w like this is definitely losing some of the elegance!

Originally Posted by JimmyHAD

That is what I use. Made in Minnesota. For those of use in the USA, buy American. The job you save may be your own.

Originally Posted by fccexpert

Okay......

These are the only two posts that I read in this thread.

As a Polymath I found the others, well...you know.

wtf is Polymath?

and since when does it take a whole sheet of paper to find an angle based on the height and base width of a triangle ??

I must be missing something here (am I Polymath?)

Of course my Pythagorean theorem involves making a square with another identical triangle, then calculating IT'S area, then dividing by two.

what is it I am missing here?

Originally Posted by gratewhitehuntr

wtf is Polymath?

http://en.wikipedia.org/wiki/Polymath

and since when does it take a whole sheet of paper to find an angle based on the height and base width of a triangle ??

It doesn't. Dave was just being thorough in showing his calculations.

I must be missing something here (am I Polymath?)

The only thing missing is that we aren't finding an angle based on the height and base width of a triangle. We made one equation that gives the total angle on a straight razor whether you hone it with no tape or any reasonable number of layers of tape. Did you use three layers of tape? The equation works. Did you use no tape? it works. One layer? works.

Of course my Pythagorean theorem involves making a square with another identical triangle, then calculating IT'S area, then dividing by two.

That's the equation for the area of a triangle. 1/2 base times height.

what is it I am missing here?

Pythagorean theorem is a² + b² = c². It finds the length of the hypotenuse.

I hope this doesn't come across sarcastic - I'm just trying to answer the questions.

none of my razors have a straight spine thickness, they all have distal taper thicker at the toe, one even has a narrower width at the heel , at least 1/8" wider at the toe-(my fav, and it was made that way)

whattya do then?

Originally Posted by kevint

whattya do then?

fix it with tape?